Re: [PATCH 2.6.19 5/5] fs: freeze_bdev with semaphore not mutex

From: Pavel Machek
Date: Wed Nov 15 2006 - 17:50:09 EST

Hi!

> > > > There's one more thing, actually. If the on-disk data and metadata are
> > > > changed _after_ the sync we do and _before_ we create the snapshot image,
> > > > and the subsequent resume fails,
> > >
> > > Well, but this is equivalent to a power failure immediately after the sync, so
> > > there _must_ be a way to recover the filesystem from that, no?
> >
> > Exactly.
> >
> > > I think I'll prepare a patch for freezing the work queues and we'll see what
> > > to do next.
> >
> > Thanks!
>
> Okay, the patch follows.
>
> I've been running it for some time on my boxes and it doesn't seem to break
> anything. However, I don't use XFS, so well ...

Seems like a way to go, thanks!
Pavel

> Index: linux-2.6.19-rc5-mm2/include/linux/workqueue.h
> ===================================================================
> --- linux-2.6.19-rc5-mm2.orig/include/linux/workqueue.h 2006-09-20 05:42:06.000000000 +0200
> +++ linux-2.6.19-rc5-mm2/include/linux/workqueue.h 2006-11-15 21:58:40.000000000 +0100
> @@ -55,9 +55,11 @@ struct execute_work {
> } while (0)
>
> extern struct workqueue_struct *__create_workqueue(const char *name,
> - int singlethread);
> -#define create_workqueue(name) __create_workqueue((name), 0)
> -#define create_singlethread_workqueue(name) __create_workqueue((name), 1)
> + int singlethread,
> + int freezeable);
> +#define create_workqueue(name) __create_workqueue((name), 0, 0)
> +#define create_freezeable_workqueue(name) __create_workqueue((name), 0, 1)
> +#define create_singlethread_workqueue(name) __create_workqueue((name), 1, 0)
>
> extern void destroy_workqueue(struct workqueue_struct *wq);
>
> Index: linux-2.6.19-rc5-mm2/kernel/workqueue.c
> ===================================================================
> --- linux-2.6.19-rc5-mm2.orig/kernel/workqueue.c 2006-11-15 21:32:13.000000000 +0100
> +++ linux-2.6.19-rc5-mm2/kernel/workqueue.c 2006-11-15 22:27:40.000000000 +0100
> @@ -31,6 +31,7 @@
> #include <linux/mempolicy.h>
> #include <linux/kallsyms.h>
> #include <linux/debug_locks.h>
> +#include <linux/freezer.h>
>
> /*
> * The per-CPU workqueue (if single thread, we always use the first
> @@ -57,6 +58,8 @@ struct cpu_workqueue_struct {
> struct task_struct *thread;
>
> int run_depth; /* Detect run_workqueue() recursion depth */
> +
> + int freezeable; /* Freeze the thread during suspend */
> } ____cacheline_aligned;
>
> /*
> @@ -251,7 +254,8 @@ static int worker_thread(void *__cwq)
> struct k_sigaction sa;
> sigset_t blocked;
>
> - current->flags |= PF_NOFREEZE;
> + if (!cwq->freezeable)
> + current->flags |= PF_NOFREEZE;
>
> set_user_nice(current, -5);
>
> @@ -274,6 +278,9 @@ static int worker_thread(void *__cwq)
>
> set_current_state(TASK_INTERRUPTIBLE);
> while (!kthread_should_stop()) {
> + if (cwq->freezeable)
> + try_to_freeze();
> +
> add_wait_queue(&cwq->more_work, &wait);
> if (list_empty(&cwq->worklist))
> schedule();
> @@ -350,7 +357,7 @@ void fastcall flush_workqueue(struct wor
> EXPORT_SYMBOL_GPL(flush_workqueue);
>
> static struct task_struct *create_workqueue_thread(struct workqueue_struct *wq,
> - int cpu)
> + int cpu, int freezeable)
> {
> struct cpu_workqueue_struct *cwq = per_cpu_ptr(wq->cpu_wq, cpu);
> struct task_struct *p;
> @@ -360,6 +367,7 @@ static struct task_struct *create_workqu
> cwq->thread = NULL;
> cwq->insert_sequence = 0;
> cwq->remove_sequence = 0;
> + cwq->freezeable = freezeable;
> INIT_LIST_HEAD(&cwq->worklist);
> init_waitqueue_head(&cwq->more_work);
> init_waitqueue_head(&cwq->work_done);
> @@ -375,7 +383,7 @@ static struct task_struct *create_workqu
> }
>
> struct workqueue_struct *__create_workqueue(const char *name,
> - int singlethread)
> + int singlethread, int freezeable)
> {
> int cpu, destroy = 0;
> struct workqueue_struct *wq;
> @@ -395,7 +403,7 @@ struct workqueue_struct *__create_workqu
> mutex_lock(&workqueue_mutex);
> if (singlethread) {
> INIT_LIST_HEAD(&wq->list);
> - p = create_workqueue_thread(wq, singlethread_cpu);
> + p = create_workqueue_thread(wq, singlethread_cpu, freezeable);
> if (!p)
> destroy = 1;
> else
> @@ -403,7 +411,7 @@ struct workqueue_struct *__create_workqu
> } else {
> list_add(&wq->list, &workqueues);
> for_each_online_cpu(cpu) {
> - p = create_workqueue_thread(wq, cpu);
> + p = create_workqueue_thread(wq, cpu, freezeable);
> if (p) {
> kthread_bind(p, cpu);
> wake_up_process(p);
> @@ -657,7 +665,7 @@ static int __devinit workqueue_cpu_callb
> mutex_lock(&workqueue_mutex);
> /* Create a new workqueue thread for it. */
> list_for_each_entry(wq, &workqueues, list) {
> - if (!create_workqueue_thread(wq, hotcpu)) {
> + if (!create_workqueue_thread(wq, hotcpu, 0)) {
> printk("workqueue for %i failed\n", hotcpu);
> return NOTIFY_BAD;
> }
> Index: linux-2.6.19-rc5-mm2/fs/xfs/linux-2.6/xfs_buf.c
> ===================================================================
> --- linux-2.6.19-rc5-mm2.orig/fs/xfs/linux-2.6/xfs_buf.c 2006-11-15 21:32:08.000000000 +0100
> +++ linux-2.6.19-rc5-mm2/fs/xfs/linux-2.6/xfs_buf.c 2006-11-15 22:12:43.000000000 +0100
> @@ -1826,11 +1826,11 @@ xfs_buf_init(void)
> if (!xfs_buf_zone)
> goto out_free_trace_buf;
>
> - xfslogd_workqueue = create_workqueue("xfslogd");
> + xfslogd_workqueue = create_freezeable_workqueue("xfslogd");
> if (!xfslogd_workqueue)
> goto out_free_buf_zone;
>
> - xfsdatad_workqueue = create_workqueue("xfsdatad");
> + xfsdatad_workqueue = create_freezeable_workqueue("xfsdatad");
> if (!xfsdatad_workqueue)
> goto out_destroy_xfslogd_workqueue;
>

--
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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